A storage apparatus connected to a host computer via a network, as a storage device storing data, for example, comprises multiple magnetic disks. The storage apparatus, by the technology of RAID (Redundant Array of Independent (or Inexpensive) Disks), makes the storage areas of the multiple storage devices redundant and configures a RAID group. Furthermore, the storage apparatus, to the host computer, provides the storage area of the capacity required by the host computer from a part of the RAID group in the form of logical volumes. Generally, logical volumes of the storage apparatus are configured of high-performance and expensive storage devices, configured of low-performance and inexpensive storage devices, or configured of different degrees of redundancy of the RAID configuration, and are used differently depending on usage.
Furthermore, for the storage apparatus, the technology of Thin Provisioning exists. Thin Provisioning is the technology in which [the storage apparatus], instead of providing logical volumes as a storage area in a fixed capacity to the host computer, provides virtual logical volumes (virtual volumes) to the host computer and, in accordance with the data write processing and others from the host computer to the storage apparatus, from a storage area (pool) created of multiple logical volumes, by assignment units of the storage area called pages, assigns storage areas to the virtual volumes. By using the Thin Provisioning technology, the storage capacity to be provided to the host computer can be dynamically extended.
Here, a page is a storage area created by splitting a logical volume configuring the pool (pool volume) by the appropriate capacity with a logical block address (LBA (Logical Block Address)). A page may also be referred to as a segment. Meanwhile, an LBA is the address used, when the host computer reads/writes data from/to the storage apparatus, for specifying the data read/write location in the logical volume provided to the host.
A technology of performing efficient operations in a pool configured of pool volume groups of different performances is proposed (refer to Patent Literature 1). In this technology, the management server or the storage apparatus monitors the access status (e.g. the number of times of read/write per unit of time (IOPS) and others) of each page assigned to the virtual volumes. With reference to the access status of the monitored pages, the pages of high frequencies of use are dynamically migrated to the storage area in the pool volume configured of expensive and highly-reliable storage devices, and the pages of low frequencies of use are dynamically migrated to the storage area in the pool volume configured of low-cost storage devices. By this method, the deterioration of the performance and reliability of the virtual volume and the increase of the operation cost of the storage apparatus can be prevented.
Meanwhile, a storage system wherein, for example, in addition to a first storage apparatus comprising a first storage device storing data whose access frequency is high and others, a second storage apparatus comprising a second storage device storing data whose access frequency is low and others is installed, the first storage apparatus and the second storage apparatus are connected via the communication network and, if the first storage apparatus receives a first data input/output request from the host computer and determines that the first data input/output request is not assigned to the same, [the first storage apparatus] converts the first data input/output request into a second data input/output request and sends the converted second data input/output request to the second storage apparatus via the communication network, and the second storage apparatus, in accordance with the second data input/output request, performs the data input/output processing for the second storage device is proposed (refer to Patent Literature 2).
By using the technology described in Patent Literature 2, what is called an externally connected function, even in the cases where a new storage apparatus is installed in [addition to] an existing storage apparatus, the old storage apparatus can be efficiently utilized without any specification change or modification.
Here, in configuring a storage system including the first storage apparatus and the second storage apparatus, by registering the logical volumes configured of the first storage devices belonging to the first storage apparatus in the pool as internal logical volumes and registering the logical volumes configured of the second storage devices belonging to the second storage apparatus in the pool as external logical volumes, the pool in which the internal logical volumes and the external logical volumes are mixed can be configured.
That is, in configuring the storage system including the first storage apparatus and the second storage apparatus, by combining the technology described in Patent Literature 1 and the technology described in Patent Literature 2, to each page to which an internal logical volume or an external logical volume is assigned, it is possible to assign the storage area of the same to the virtual volumes, and it is also possible to perform the appropriate page allocation complying with the characteristic of the media.